1. Technical Field
The present invention relates to an electrophotographic transfer device and an image forming apparatus that transfer an image from an image carrier to a transfer medium such as paper, using a transfer roller in pressing-contact with the image carrier carrying the image to be transferred.
2. Related Art
In a wet type image forming apparatus that uses liquid developer, because a transfer surface on a toner image side of a transfer medium such as paper is in pressing-contact with an intermediate transfer medium, the transfer medium is liable to stick to the intermediate transfer medium after a transfer. In connection to this, to date, an image forming apparatus in which the transfer medium is separated from the transfer roller by blowing air onto the edge of the transfer medium after a transfer has been proposed (see, for example, Japanese Patent No. 3128067).
On the other hand, among image forming apparatuses that use a dry type developer, an image forming apparatus in which a toner image of a photoreceptor is transferred to a transfer medium in a state in which the edge of the transfer medium is gripped by grippers of a transfer drum that is in pressing-contact with the photoreceptor has been proposed (see, for example, JP-A-3-4241). By performing the transfer in a state in which the edge of the transfer medium is gripped, the transfer medium is easily separated from the photoreceptor after the transfer.
However, in the image forming apparatus described in the above-referenced Japanese Patent No. 3128067, it is difficult to securely perform separation of the transfer medium because the air is simply blown onto the edge of the transfer medium.
Consequently, the technique of separating the edge of the transfer medium by gripping described in JP-A-3-4241 can be applied to the image forming apparatus using the liquid developer described in Japanese Patent No. 3128067. However, because the transfer drum having the transfer medium gripping member described in JP-A-3-4241 is rotating during the transfer operation, it is difficult to grip the transfer medium at a fixed position securely and stably, the transfer medium being transported toward the transfer drum. In the image forming apparatus described in JP-A-3-4241, no consideration is given at all of how the transfer medium gripping member, which is in motion, should securely and stably grip the transfer medium at a fixed position on the transfer medium.
Therefore, it is difficult to perform excellent image formation even if the technique for separating the transfer medium described in JP-A-3-4241 is applied to the image forming apparatus described in Japanese Patent No. 3128067.